I think it's really tough to say whether Huckabee is some kind of problematic liberal. We give Mitt a pass for a lot of things because he was in a blue state, but you have to remember that Huckabee cut his teeth campaigning in a blue/purple state.
He plays to the middle because he has good instincts for a general election campaign. His rhetoric tilts centrist, but I suspect he'd be net positive for us. His weight loss and health stuff will be eaten up by Americans who probably yearn for that kind of thing that everyone can get behind and feel good about.
Huck would probably make the GOP a more populist party and would probably actually broaden its support. The question is whether he'd do so at the expense of bad policy initiatives. I tend to think he'd be like a more virtuous Clinton. Wouldn't accomplish a lot policy-wise, but would be a good face for the party.